500 ml of a solution contain 12.6 grams of oxalic acid [Mol. Mass = 126 g/mole]. 10 ml of this solution is diluted to 100 ml in a flask. What is the molarity of the resultant solution?

Options

A. 0.1
B. 0.2
C. 0.01
D. 0.02

Answer

To find the molarity of the resultant solution after diluting 10 ml of the original solution to 100 ml, we can follow these steps:

### Step 1: Calculate the number of moles of oxalic acid in the original solution.
- Given mass of oxalic acid = 12.6 grams
- Molar mass of oxalic acid = 126 g/mole

Using the formula:
\[ \text{Number of moles} = \frac{\text{Given mass}}{\text{Molar mass}} = \frac{12.6 \text{ g}}{126 \text{ g/mole}} = 0.1 \text{ moles} \]

### Step 2: Calculate the molarity of the original 500 ml solution.
- Volume of the solution = 500 ml = 0.5 L

Using the formula for molarity:
\[ \text{Molarity (M)} = \frac{\text{Number of moles}}{\text{Volume in liters}} = \frac{0.1 \text{ moles}}{0.5 \text{ L}} = 0.2 \text{ M} \]

### Step 3: Use dilution formula to find the molarity of the diluted solution.
- Initial volume (V1) = 10 ml = 0.01 L
- Final volume (V2) = 100 ml = 0.1 L
- Initial molarity (M1) = 0.2 M
- Final molarity (M2) = ?

Using the dilution formula:
\[ M_1 V_1 = M_2 V_2 \]
Substituting the known values:
\[ 0.2 \text{ M} \times 0.01 \text{ L} = M_2 \times 0.1 \text{ L} \]

### Step 4: Solve for M2.
\[ 0.002 = M_2 \times 0.1 \]
\[ M_2 = \frac{0.002}{0.1} = 0.02 \text{ M} \]

### Final Answer:
The molarity of the resultant solution is **0.02 M**.

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